The invention is directed to a jet device for concentrating or compressing gaseous media for use in metallurgical or chemical processes. The jet device having a driving nozzle which is arranged centrically in a jet head and directed toward a mixing chamber with which a pressure nozzle is connected coaxially.
Such jet compressors are used particularly for jet degasification in metallurgy plants. Steam jet pumps are essentially used for this purpose. Since the vacuum required for jet degasification cannot be achieved by a single-stage jet device, a multi-stage jet device is used.
A steam jet pump having a jet head with a driving nozzle projecting into the latter is known from "die Vakuumbehandlung des flussigen Stahles [vacuum processing of molten steel]" by W. Coupette, R. A. Lang Verlag 1967, page 77. Also, a jet compressor which is constructed in a comparable manner, at least up to the mixing chamber, is known from DE-OS 30 05 653.
In jet compressors of the kind known from the aforementioned texts, steam is used as a driving medium. The steam is lined to the steam jet pump via the driving medium feed line, a Laval nozzle being connected to the end of the latter. The enthalpy of the steam is transformed virtually completely into kinetic energy by this nozzle. The steam enters the above-mentioned mixing chamber at ultrasonic speed, where it encounters the medium which is to be conveyed by the steam and which flows at a lesser speed. Due to the friction effect in the long Laval nozzle, a boundary layer is formed at the wall of the Laval nozzle and occupies a considerable portion of the nozzle cross section, particularly in the use regions range of application of lesser densities, corresponding to a suction pressure of approximately 1 mbar. This boundary layer represents considerable losses and slows down the turbulent mixing process at the output of the nozzle, i.e. in the region of the mixing zone. This in turn leads to a lengthening of the mixing chamber and consequently to friction losses.
A diffusion pump whose nozzle has outflow openings in the shape of annular gaps is known from DE-OS 25 50 456.
In the pump known from the above-cited text, oil vapor is used as a driving medium, its flow direction being turned by 180.degree.. The roof arranged at the outlet of the driving-medium feed line serves as a baffle plate.
The annular-gap nozzles of the jet device known from this text are unsuitable, both in form and in capacity, for industrial-scale metallurgical and chemical processes.